1. Field of the Invention
The present invention relates to an apparatus and method for using a mixture of waste oil and fresh fuel oil as fuel for a diesel engine, and more particularly to an apparatus and method whereby a diesel engine can be run using a heated oil-fuel mixture that is less than five percent fresh fuel oil.
2. Description of the Related Art
It has been previously known to dispose of waste oil by mixing a small percentage of the waste oil with diesel fuel and burning the mixture in a diesel engine. For example, U.S. Pat. No. 5,507,307 to Montegari et al. discloses a method and apparatus for recycling waste lubricating oil for reuse as fuel oil wherein waste oil is blended with fuel oil, the mixture being from zero to ten percent waste oil. U.S. Pat. No. 4,095,571 to Fleetwood et al. discloses a filtering and mixing apparatus for automatically removing used lubricating oil from the sump of an engine and combining the oil with the engine""s fuel supply. It is stated that the ratio of lubricating oil to fuel oil does not exceed five percent.
Waste oil has been combined with fuel oil in higher concentrations for use as fuel in furnaces or steam boilers, however these applications are not as sensitive to the presence of contaminants or to the viscosity of the fuel as is a diesel engine. The fuel injectors of a diesel engine are easily clogged or eroded by contaminated fuel.
Disposal of waste oil is an increasing environmental problem and it would clearly be advantageous to be able to reclaim more of this troublesome substance and convert it into useful energy by using it as fuel for diesel engines at higher concentrations.
The present invention comprises an apparatus and method for reclaiming waste oil for use as fuel for a diesel engine. The apparatus includes a mixing tank, a waste oil transfer pump which supplies waste oil to the mixing tank, and a fuel proportioning pump which supplies a proportional amount of light fuel oil to the mixing tank to form an oil-fuel mixture. The apparatus may also include an additive proportioning pump which supplies chemical fuel additives such as emulsifiers and combustion improvers to the mixing tank. A heating unit is installed in the mixing tank for purposes of heating the oil-fuel mixture in order to control the viscosity of the mixture. A fuel delivery pump delivers the heated oil-fuel mixture from the mixing tank to a diesel engine for use as fuel.
The apparatus also includes two sets of filters for removing contaminants. A set of pre-filters removes a large portion of the particulate material from the waste oil before it is delivered to the mixing tank, and a set of final filters removes additional contaminants from the oil-fuel mixture before it reaches the engine.
The waste oil transfer pump, fuel proportioning pump, and additive proportioning pump are electrically powered, and are controlled by a fluid level switch associated with the mixing tank. When the level of oil-fuel mixture in the tank drops to a low condition, the fluid level switch closes which causes the pumps to begin operating, thereby supplying the correct proportions of waste oil, fuel oil, and additives to the mixing tank. When the level of oil-fuel mixture reaches a full condition, the switch opens, shutting off the pumps.
In order to match the output of the fuel delivery pump to the requirements of the diesel engine, the apparatus includes a bypass valve installed in the fuel line between the final filters and the diesel engine. The bypass valve directs the amount of the oil-fuel mixture required by the engine injection pump into the engine fuel supply line and recirculates the excess back to the mixing tank.
Because the diesel engine can be difficult to start using an oil-fuel mixture with a high percentage of waste oil, the apparatus also includes a start valve, which can selectively switch the engine over to a supply of fresh fight fuel oil during starting. After the engine is running, it can be switched back to the oil-fuel mixture.
The method for reclaiming waste oil for use as fuel for a diesel engine comprises the steps of collecting and storing a supply of waste oil; mixing the waste oil with light fuel oil to form an oil-fuel mixture; heating the oil-fuel mixture; and delivering the heated oil-fuel mixture to a diesel engine for use as fuel. The mixing step can optionally include adding chemical additives such as emulsifiers and combustion improvers to the oil-fuel mixture. Filtering steps can be included before the mixing step and/or between the heating step and the delivering step.
The principal objects and advantages of the present invention include: providing an apparatus and method for reclaiming waste oil for use as fuel for a diesel engine; providing such an apparatus and method which allow a diesel engine to run on oil-fuel mixtures having as little as five percent fresh light fuel oil content; and providing such an apparatus which is economical to manufacture, efficient in operation, capable of long operating life and particularly well-adapted for the proposed usage thereof.